title: The effect of simulated obstructive apnea and hypopnea on aortic diameter and BP.
abstract: BACKGROUND
  Preliminary evidence supports an association between obstructive sleep apnea (OSA) and thoracic aortic dilatation. The mechanisms through which OSA may promote thoracic aortic dilatation are incompletely understood. Therefore, we studied the acute effects of simulated apnea and hypopnea on aortic diameter and BP in humans.
  
  
  METHODS
  The diameter of the aortic root was measured in 20 healthy volunteers by echocardiography, and peripheral BP was continuously recorded prior, during, and immediately after simulated obstructive hypopnea (inspiration through threshold load), simulated obstructive apnea (Müller maneuver), end-expiratory central apnea, and normal breathing in randomized order.
  
  
  RESULTS
  Proximal aortic diameter increased significantly during inspiration through a threshold load (+6.48%; SE, 3.03; P = .007), but not during Müller maneuver (+3.86%; SE, 2.71; P = .336) or end-expiratory central apnea (+0.62%; SE, 2.94; P = .445). Maneuver-induced changes in mean BP were observed during inspiration through a threshold load (-10.5 mm Hg; SE, 2.2; P < .001), the Müller maneuver (-8.8 mm Hg; SE, 2.4; P < .001), and end-expiratory central apnea (-4.2 mm Hg; SE, 1.4; P = .052). There was a significant increase in mean BP on release of threshold load inspiration (+8.1 mm Hg; SE, 2.9 mm Hg; P = .002), Müller maneuver (+10.7 mm Hg; SE, 2.9; P < .001), and end-expiratory central apnea (+10.6 mm Hg; SE, 2.5; P < .001).
  
  
  CONCLUSIONS
  Simulated obstructive hypopnea/apnea and central apnea induced considerable changes in BP, and obstructive hypopnea was associated with an increase in proximal aortic diameter. Further studies are needed to investigate effects of apnea and hypopnea on transmural aortic pressure and aortic diameter to define the role of OSA in the pathogenesis of aortic dilatation.
authors.affiliation: Sleep Disorders Center and Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Anne-Christin
authors.initials: AC
authors.lastname: Stöwhas
authors.affiliation: Division of Cardiology, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Namdar
authors.affiliation: Division of Cardiology, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Patric
authors.initials: P
authors.lastname: Biaggi
authors.affiliation: Sleep Disorders Center and Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
authors.forename: Erich W
authors.initials: EW
authors.lastname: Russi
authors.affiliation: Sleep Disorders Center and Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
authors.affiliation: Oxford Center for Respiratory Medicine, Churchill Hospital, Oxford, England.
authors.forename: John R
authors.initials: JR
authors.lastname: Stradling
authors.affiliation: Sleep Disorders Center and Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland. Electronic address: Malcolm.K@bluewin.ch.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001013:Aorta, Thoracic / Q000473:pathology*; D001794:Blood Pressure / Q000502:physiology*; D004108:Dilatation, Pathologic; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D055815:Young Adult